This invention is related generally to light modulating systems and is more particularly concerned with a novel device for direct integration into a optical fiber communications system in which modulation is accomplished within the fiber optic waveguide.
The use of "light" frequency electromagnetic energy for communication purposes has been recently brought much closer to reality through the production of extremely low loss optical fibers and the extension of continuous wave (CW) room temperature operation of diode lasers to over 10,000 hours. The new optical fibers exhibit approximately 2 db of loss per kilometer.
For optical fiber communications system to become a practical reality, other efficiencies within the system must also be greatly improved. For example, whenever the waveguide undergoes a configurational transition, a loss in efficiency occurs. Furthermore, whenever conversion is required between electrical and optical forms of energy, considerable loss of efficiency is experienced.
For light to be utilized as a communication vehicle in an all cylindrical optical fiber waveguide system, it is necessary that the light be modulated in some manner. Furthermore, it is necessary that the modulation technique be sufficiently fast so that practical data rates are achieved. Such data rates cannot be achieved by direct modulation of a laser source such as by modulating the exciting energy source.
Therefore, direct incorporation of a laser into an optical fiber waveguide cannot per se solve the modulation problem.
Many electro-optic, magneto-optic and acoousto-optic modulation mechanisms have been evolved for use in a planar optical waveguide configuration. However, as mentioned previously, a distinct loss in efficiency occurs when light is coupled from a circular optical fiber waveguide, which is conceded to be the only commercially feasible transmission waveguide, into a planar waveguide.